Dual motorcycle exhaust system

ABSTRACT

An exhaust system for an internal combustion engine having a first cylinder and a second cylinder from which pulses of exhaust gas exit and are routed along separate paths towards the exhaust mufflers. The exhaust system independently routes the pulses of exhaust gas from the two cylinders. The exhaust gases that are expelled from the first cylinder are routed through a first exhaust pipe. The exhaust gases that are expelled from the second cylinder are routed through a second exhaust pipe assembly. The second exhaust pipe assembly routes the exhaust gasses from an exhaust port for the second cylinder laterally across the motorcycle to achieve a true dual exhaust system. The second exhaust pipe assembly provides an approximate equal length flow path as compared to the path used by the exhaust gasses that are expelled from the first cylinder.

RELATED APPLICATIONS

This application is a continuation of copending patent application Ser.No. 10/968,380, filed Oct. 18, 2004, and titled DUAL MOTORCYCLE EXHAUSTSYSTEM, which is a continuation of patent application Ser. No.10/255,131, filed Sep. 25, 2002, and titled DUAL MOTORCYCLE EXHAUSTSYSTEM, now U.S. Pat. No. 6,804,955 which issued on Oct. 19, 2004, whichclaims the benefit of U.S. Provisional Patent Application Ser. No.60/326,026, entitled TRUE DUAL MOTORCYCLE EXHAUST SYSTEM, filed Sep. 26,2001, the disclosures of which are hereby incorporated by reference intheir entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to exhaust systems. More particularly,the invention relates to an exhaust system for a multi-cylinder internalcombustion engine.

2. Background

Motorcycles commonly employ exhaust systems to convey the exhaust gasfrom the engine's cylinder to the ambient environment. The journeybegins at the engine cylinder, which incorporates intake and exhaustports for ingress and egress to the cylinder. Fresh air mixed with fuelenters the engine cylinder through the intake port where it issubsequently compressed by a piston and ignited. A rapid expansion ofthe compressed fuel and air occurs, thereby forcefully moving the pistonin the opposite direction to the compression stroke. Once the expansionis complete, the exhaust port opens to allow the combustion by-productsor gas to exit the engine cylinder and enter an exhaust pipe. Theexhaust port may be a passageway into the engine cylinder that isuncovered by the retreating piston, as in a two-stroke design well knownin the art. In the case of a four-stroke design, a valve is utilized toopen or close the exhaust port. The exhaust gas expelled from the enginecylinder, after passing through the exhaust port, enters an exhaustpipe. The exhaust pipe is designed to direct the exhaust gas towards therear of the motorcycle and commonly utilizes bends and curves toaccomplish this goal.

In the case of a V-Twin Harley-Davidson® motorcycle engine, the designof the stock OEM exhaust system affects the motorcycle's performance.The OEM exhaust system comprises a partial dual exhaust system withunequal length exhaust pipes from each cylinder. This system allows somecommunication between the exhaust gases from the cylinders via acrossover pipe. However, the design of this crossover pipe isdetrimental to the engine's performance. The exhaust gases from thecylinders interfere with each other as they are routed to two exhaustmufflers. Moreover, the routing path of the gases from the engineexhaust ports to the exhaust mufflers increases the exhaust systemsbackpressure.

The design of the stock OEM exhaust system for the V-TwinHarley-Davidson® motorcycle also affects the aural sensation experiencedby the rider. For example, the sound of the OEM exhaust system is unevenas heard by the rider due to the exhaust system's design. Further,during the engine's transition from under load to a state ofdeceleration, the engine emits a staccato popping sound that is notpleasing to the ear. Any potential aftermarket fix for these performanceand aural sensation issues is further complicated by the design of theHarley-Davidson® OEM exhaust system which attaches to the chassis of themotorcycle at fixed points, thus impeding any modifications to theexhaust system without permanent changes to the motorcycle.

SUMMARY OF THE INVENTION

One embodiment of the present invention is an exhaust system for aV-Twin motorcycle engine. This embodiments provides a substantialimprovement to the well-known Harley-Davidson® engine.

One aspect of the aftermarket exhaust system constructed in accordancewith one embodiment of the present invention is an exhaust system whichcomprises a first exhaust port in communication with a first cylinder ofthe engine to discharge a first pulse of exhaust gas, a second exhaustport in communication with a second cylinder of the engine to dischargea second pulse of exhaust gas, wherein the first and second exhaustports are both located on a first side of the V-Twin engine. The systemfurther comprises a first exhaust pipe having an inlet end and an outletend, wherein the inlet end is connected to the first exhaust port forscavenging and routing the first pulse of exhaust gas along the firstside and in a direction aft of the motorcycle chassis, a second exhaustpipe having an inlet end and an outlet end, wherein the inlet end isconnected to the second exhaust port for scavenge and routing the secondpulse of exhaust gas through the motorcycle chassis and along a secondside of the V-Twin engine in a direction aft of the motorcycle chassis,wherein the first and second sides are substantially parallel with themotorcycle chassis, and wherein the second exhaust pipe utilizes an OEMattachment point to the motorcycle chassis. The system still furthercomprises a first muffler connected to and in flow communication withthe first exhaust pipe, wherein the first pulse of exhaust gas isexpelled through the first muffler to the atmosphere, and a secondmuffler connected to and in flow communication with the second exhaustpipe, wherein the second pulse of exhaust gas is expelled through thesecond muffler to the atmosphere.

Another aspect of the present invention is a motorcycle with a twocylinder V-Twin engine and a true dual exhaust system wherein the truedual exhaust system individually routes exhaust gases from the twocylinders to a pair of mufflers.

Still another aspect of the present invention is a motorcycle thatcomprises a frame, a V-twin engine attached to the frame and having afirst and a second cylinder head, each containing a cylinder, whereinthe first and second cylinder heads exhaust gas on a same side of theV-twin engine, and a dual exhaust system in flow communication with thetwo cylinder heads and configured to route exhaust gases from the twocylinders, to different sides of the frame, and to the atmosphere.

Yet another aspect of the present invention is an exhaust systemcomponent for a Harley-Davidson® motorcycle with a V-Twin engine,wherein the V-twin engine comprises first and second exhaust ports, bothlocated on a first side of the V-twin engine, and wherein the secondexhaust port is located rearward of the first exhaust port. The exhaustsystem component comprises an exhaust pipe having an inlet end and anoutlet end, wherein the inlet end is configured to route exhaust gasesfrom the second exhaust port and through the motorcycle and along asecond side of the V-Twin engine in a direction rearward of themotorcycle, wherein the first and second sides are substantiallyparallel with the motorcycle, and wherein the exhaust pipe utilizes anOEM attachment point to the motorcycle.

Still another aspect of the present invention is a method of processingexhaust gases from a V-Twin engine in a motorcycle, wherein a firstpulse of exhaust gas is produced in a first cylinder of the V-Twinengine and a second pulse of exhaust gas is produced in a secondcylinder of the V-Twin engine. The method comprises routing the firstpulse of exhaust gas from the first cylinder and along a first side ofthe V-Twin engine, wherein the first cylinder exhausts the first pulseof gas on the first side of the V-Twin engine, and routing the secondpulse of exhaust gas from the second cylinder and along the first sideof the V-Twin engine and back under a seat of the motorcycle to a secondside of the V-Twin engine, wherein the second cylinder exhausts thesecond pulse of gas on the first side of the V-Twin engine, and whereinthe first pulse of exhaust gas and the second pulse of exhaust gasfollow different flow paths.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, objectives, and advantages of the embodiments of theinvention will become more apparent from the detailed description setforth below when taken in conjunction with the drawings wherein likeparts are identified with like reference numerals throughout, andwherein:

FIG. 1 is a top plan view showing an exhaust system according to oneembodiment of the invention.

FIG. 2 is a side perspective view of an upstream pipe shown in FIG. 1 inaccordance with one embodiment of the invention.

FIG. 3 is a top plan view showing a Harley-Davidson® OEM exhaust system.

FIG. 4 is a side perspective view of a Harley-Davidson® motorcycleincorporating the upstream pipe into its OEM exhaust system.

FIG. 5 is a side perspective view of a portion of the motorcycle exhaustsystem encompassed within line 5 of FIG. 4 and shows the upstream pipeof the present invention connected to a cylinder.

FIG. 6 is a side perspective view of the upstream pipe from FIG. 2,taken on the opposite side of the motorcycle to that of FIG. 4.

FIG. 7 is a front perspective view of the upstream pipe shown in FIG. 2as installed on the motorcycle of FIG. 4.

FIG. 8 is a rear perspective view of the upstream pipe shown in FIG. 2as installed on the motorcycle of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

In a single cylinder engine, the exhaust gas, after passing through theexhaust pipe, is typically fed into a muffler prior to its expulsioninto the atmosphere to dissipate unwanted noise originating in thecombustion process. The exhaust system may also include a catalyticconverter or other exhaust treatment device well known in the art. Themuffler design will significantly affect the audible noise level orsound of the engine. A manufacturer can attenuate or change the sound ofthe engine so as to not only meet governmental noise requirements butalso for the engine to exhibit a pleasing sound to the ear.

Depending on the design of the exhaust system, including the muffler andexhaust pipe, back pressure will be introduced into the exhaust system.Back pressure impedes the free flow of exhaust gases along the exhaustsystem's entire length. For example, in a four-stroke engine the pistonpushes the exhaust gases out of the cylinder and into the exhaustsystem. If the back pressure in the exhaust system is reduced, thepiston requires less force to expel the exhaust gases from the enginecylinder thereby increasing the performance and efficiency of theengine.

The performance of an engine is measured by the engine's generation of,for example, horsepower and torque. These two values can be measuredover the entire RPM operating range as well as their peak values.Generally, less back pressure will enhance the performance of the engineby increasing the engine's efficiency. This rise in efficiency canfurther reduce the engine's fuel consumption. However, a significantreduction in back pressure, which may be accomplished by, for example,using short exhaust pipes and no muffler, may have an adverse effect onengine noise and overall performance. An exhaust system design thatmaximizes the horsepower of an engine will often have a deleteriouseffect on the engine's torque production over a portion of the RPMrange. If this drop in torque is located in the middle of the RPM range,it may be noticeable as a momentary drop in acceleration to the rider ordriver and be undesirable.

The overall length and shape of the exhaust system is an importantfactor in determining how the engine will operate and affects theperformance of the engine. For example, with a multi-cylinder engine therouting of the individual exhaust systems for each cylinder will affectflow turbulence. Flow turbulence can be caused by pulses of exhaust gasfrom the different cylinders combining before being expelled to theatmosphere.

Moreover, the geometry of the exhaust ports by which the exhaust isexpelled form the engine cylinders, may also hamper the design of theexhaust system. Furthermore, the design of an exhaust system is alsoaffected by cost, size, weight, and packaging limitations. This concernis especially acute for a motorcycle since the exhaust system needs tofit close to the motorcycle frame so that the rider and passenger canstraddle the motorcycle and not be subjected to burns or the like causedby contact with the hot exhaust system. An automobile is less prone tothe concern for unwanted contact with the exhaust system as the car'sfloorpan is a barrier between the exhaust system and the occupants. Amotorcycle, in a similar fashion, can incorporate heat shields to coverthe exhaust system to further protect the rider/passenger from the hotexhaust system. This heat shield may also act as a sound barrier toreduce the noise associated with the exhaust system. For an automobile,the length of the exhaust system may be increased to help dampen out theengine noise originating in the combustion process, but this may not bewell suited for a motorcycle due to a motorcycle's relatively shortlength as compared to an automobile.

Exhaust systems are commonly routed along the sides or below themotorcycle depending on such design factors as, for example, theorientation of the engine cylinders with respect to one another, theorientation of the engine in the motorcycle frame, the preferred ridingcharacteristics, aesthetics, the size of the motorcycle, and thelocation of the motorcycle's center of gravity. A motorcycle with atransverse engine to its frame may be able to route its exhaust systembelow the engine and frame without increasing the overall width of themotorcycle. The cylinders of a transverse engine are often located atsimilar distances from the mufflers, which simplifies designing an equallength exhaust system.

A motorcycle with an engine inline with the frame, for example, aninline “V” configuration, may be able to route its exhaust system alongboth sides of the motorcycle due to its narrower width. However, in suchan arrangement, the engine cylinders will not be located at similardistances from the mufflers. This configuration causes some of theexhaust gases to travel a longer distance prior to being expelled to theatmosphere. The location of each exhaust port around the circumferenceof its associated cylinder may also increase the difficulty in designingan exhaust system for an inline engine.

As a result of the many tradeoffs associated with the design of anexhaust system, a manufacturer will choose an exhaust system thatpresents a compromise between these characteristics for the consumer. Asdiscussed above, these characteristics may include, for example, cost,size, weight, engine noise, aesthetics, performance, and packaginglimitations.

Customization of exhaust components by motorcycle riders, such asexhaust pipes and mufflers, is common in the aftermarket. Customizationallows the owner to re-optimize the characteristics of their vehicle soas to maximize their own satisfaction. A successful customization leadsto not only personal satisfaction of accomplishment, but also a feelingof attachment to the vehicle. Often, the replacement of a component madeby the original equipment manufacturer (OEM) with an aftermarket partdoes not live up to expectations and will not be easily reversible onceit is completed. This can lead to the owner incurring additional coststo reverse the modification. For example, the addition of a force airinduction system to an automobile often requires the cutting of a holein the hood over an engine. If the owner decided the additional noiseoutweighed the performance increase, the purchase of a new hood wouldhave to be absorbed to reverse the modification. In the case of exhaustsystems, incorporation of aftermarket components often requires cuttingand welding of the OEM exhaust system. Exhaust pipes or other parts ofthe exhaust system are often cut with subsequent welding being performedto incorporate the aftermarket component. Thus, the level of financialrisk being taken by the owner and difficulty in reversing themodification are increased.

One significant feature of embodiments of this invention is that itprovides the benefits of using a true dual exhaust system whileminimizing cost, weight and packaging issues associated with such asystem. The exhaust system allows the pulses of exhaust gas fromdifferent cylinders to be individually routed through the exhaustsystem. By individually routing the exhaust systems, the inherentdrawbacks of combining pulses of exhaust gases are avoided. Combiningthe pulses of exhaust gas incorrectly from multiple cylinders can leadto an increase in back pressure and a corresponding drop in engineperformance. In the present invention, the separation of the pulses ofexhaust gas from multiple cylinders increases the performance of theengine by enhancing scavenging. As a result, exhaust systems constructedin accordance with this invention actually increase the exit velocity ofthe exhaust gas from the engine cylinder.

Another feature of the invention is that each cylinder has substantiallyits own equal length exhaust pipe. This means each exhaust pipe isrouted between the exhaust port and the mufflers such that all of theexhaust pipes have the same overall length. The length of the exhaustpipe affects the performance of the cylinder from which the exhaust pipereceives the pulses of exhaust gas. Using equal length exhaust pipes foreach cylinder of a multi-cylinder engine allows all of the cylinders ofa multi-engine to be uniformly optimized.

Still another feature of the invention is that it emits a strong,throaty rumble typically preferred by riders of touring bikes, yet notso loud as to cause undue rider fatigue on a long road trip. Incontrast, the OEM exhaust system for the Harley-Davidson® results in anuneven sound coming from the two mufflers. Moreover, the OEM exhaustsystem exhibits an unpleasant popping sound during deceleration which isnot present when the exhaust system according to the embodimentsdisclosed herein is employed.

FIG. 1 is a top plan view showing an exhaust system according to oneembodiment of the invention. An internal combustion engine 20 has twocylinders 22, 24 arranged in-line. Each of the two cylinders 22, 24 havefixedly attached a cylinder head 26, 28 which forms two combustionchambers (not shown). Each cylinder head 26, 28 incorporates an intakeport (not shown) and an exhaust port 30, 32 for ingress and egress tothe each cylinder 22, 24. The intake ports are connected to an intakesystem (not shown) located between the cylinders 22, 24. The intakesystem mixes fresh air with fuel before they enter the engine cylinders22, 24. The mixed air and fuel is subsequently compressed by a piston(not shown) into each of the combustion chambers and ignited. A rapidexpansion of the compressed fuel and air occurs, thereby forcefullymoving the piston in the opposite direction to the compression stroke.The exhaust ports 30, 32 are located on the same side with respect to acenterline 33 through engine 20.

The ignition of the compressed fuel and air occurs in an alternatingsequence whereby one of the cylinders 22, 24 transmits a pulse ofexhaust gas followed by the transmission of another pulse of exhaust gasfrom the other cylinder 22, 24. In the embodiment shown in FIG. 1, thissequence continually repeats during the operation of the internalcombustion engine 20. Once the rapid expansion of the compressed fueland air is complete, the exhaust port 30, 32 which is in flowcommunication with the ignited engine cylinder 22, 24 opens to allow thecombustion by-products or pulse of gas to exit. The exiting pulse ofexhaust gas travels from the cylinder head 26, 28 and into a first or asecond exhaust pipe 34, 36. As illustrated in FIG. 1, the first exhaustpipe 34 receives pulses of exhaust gas from the first cylinder 22.Similarly, the second exhaust pipe 36 receives pulses of exhaust gasfrom the second cylinder 24.

The first exhaust pipe 34 has an inlet end and an outlet end. The inletend is connected to the exhaust port 30 to scavenge each pulse ofexhaust gas from engine cylinder 22. The first exhaust pipe 34 isconfigured to route the scavenged pulse of exhaust gas away from theengine 20 and towards its outlet end. The outlet end is in flowcommunication with a first muffler 38. The first muffler 38 isconfigured to exhaust the pulse of exhaust gas received from the firstexhaust pipe 34 into the atmosphere.

The second exhaust pipe 36 has an inlet end and an outlet end. The inletend is connected to the exhaust port 32 to scavenge each pulse ofexhaust gas from engine cylinder 24. The second exhaust pipe 36 isconfigured to route the scavenged pulse of exhaust gas away from theengine 20 and towards its outlet end. The outlet end is in flowcommunication with a second muffler 40. The second muffler 40 isconfigured to exhaust the pulse of exhaust gas received from the secondexhaust pipe 36 into the atmosphere.

The first and second exhaust pipes 34, 36 are approximately of equallength. This means each pulse of exhaust gas expelled from the engine 20travels approximately the same distance prior to being expelled to theatmosphere. The benefit to using equal length first and second exhaustpipes is that the pulses of exhaust gas will not arrive at the same timeat each of the mufflers 38, 40, which minimizes any aural interferencebetween the pulses. In one embodiment, the length of the first exhaustpipe 34 is within 10% of the length of the second exhaust pipe 36.

The use of approximately equal length first and second exhaust pipes, ascompared to an exhaust system that use unequal length exhaust pipes,increases the performance of the internal combustion engine 20 byenhancing scavenging. Scavenging is the process of removing the exhaustgases from the cylinders. Scavenging may be enhanced or reduceddepending on the design of the exhaust system coupled with the design ofthe internal combustion engine 20. For example, the design of aninternal combustion engine along with the engine's performance goalswill dictate the optimal length of its exhaust system. For example, anengine designed to maximize torque may require a longer exhaust systemthan the same engine if optimized for maximum horsepower. The likelyoperating range of the engine will also affect the selection of thelength of the exhaust system. Moreover, the incorrect combining ofpulses of exhaust gases from different cylinders due to exhaust lengthvariations may lead to an increase in back pressure and a correspondingdrop in engine performance.

In signal cylinder engines, the routing of the exhaust system tomaximize scavenging is simplified as compared to routing formulti-cylinder applications. Often, the exhaust ports for themulti-cylinder engine are located at varying distances from the exhaustmufflers. In such a situation, the length of the exhaust system does notoptimize the desired engine characteristic for all of the cylinders ofthe engine. To maximize the desired characteristic for all of thecylinders of the engine, the pulses of exhaust gas should travel asimilar distance prior to their expulsion into the environment. Aproperly scavenged engine will actually increase the exit velocity ofthe pulse of exhaust gas from the cylinders 22, 24.

Each pulse of exhaust gas that is exited to the atmosphere forms alow-pressure zone (not shown) in its wake. This low-pressure zonepreferentially travels back up the exhaust system towards the exhaustport to scavenge a subsequent pulse of exhaust gas. In a four-strokeengine, this reduces the force required by the piston to expel the pulseof exhaust gas from the plurality of cylinders 22, 24. For example, theuse of equal length first and second exhaust pipes 34, 36 improvesengine scavenging whereby the performance of the engine is improved.

Still referring to FIG. 1, the second exhaust pipe 36 comprises anupstream pipe 42 and a downstream pipe 44. The upstream pipe 42 is incommunication with the second exhaust port 32 and routes the pulse ofexhaust gas from a first side of the engine 20 and across the centerline33 towards a second side. As shown in FIG. 1, the upstream pipe 42 is inflow communication with the downstream pipe 44. The downstream pipe 44further routes the pulse of exhaust gas to the second muffler 40. Thewidth of the downstream pipe 44, measured in a direction that isperpendicular to centerline 33, can range between 7.185 and 8.185inches. In the embodiment illustrated in FIG. 1, the width is 7.685inches.

The operation of the upstream pipe 42 may be understood upon referenceto FIG. 2, which is a side perspective view of the upstream pipe 42 inaccordance with the invention. The upstream pipe 42 comprises a firstelbow 46 in flow communication with the exhaust port 32. The first elbow46 routes the pulse of exhaust gas away from the exhaust port 32. Thefirst elbow 46 has substantially a 2″ radius of curvature for less thana 90-degree arc. In one embodiment, the arc length ranges between 65 and75 degrees. In the embodiment illustrated in FIG. 2, the arc length is70 degrees.

The first elbow 46 is in flow communication with a second elbow 48. Thesecond elbow 48 routes the pulse of exhaust gas received from the firstelbow 46 through at least a 180 degree turn towards the centerline 33(see FIG. 1). In one embodiment, the second elbow 48 routes the pulse ofexhaust gas through a 245 degree turn. The second elbow 48 hassubstantially a 2.5″ radius of curvature for greater than the 180 degreearc. In one embodiment, the second elbow 48 is not coplanar with thefirst elbow 46.

As shown in FIG. 2, the second elbow 48 comprises a first sub-elbow 50and a second sub-elbow 52 joined at a weld 56. The first sub-elbow 50and the second sub-elbow 52 are in flow communication. The firstsub-elbow 50 has an approximate 180-degree arc while the secondsub-elbow 52 has an approximate arc length of less than 90 degrees. Inthe embodiment illustrated in FIG. 2, the second sub-elbow 52 has a 65degree arc length. In one embodiment, the first sub-elbow 50 and thesecond sub-elbow 52 are not coplanar.

Connected to and in flow communication with the second elbow 48 is athird elbow 53. The third elbow 53 routes the pulse of exhaust gas fromthe second elbow 48 and in a direction towards the centerline 33 wheninstalled (see FIG. 1). The third elbow has substantially a 2.5″ radiusfor an approximate arc length of less than 90 degrees. In the embodimentillustrated in FIG. 2, the third elbow 53 has an arc length of 75degrees. The geometry of the third elbow 53 is further illustrated inFIG. 8. The first, second, third, and fourth elbows are advantageouslyfabricated from a metallic material. For example, one embodimentutilizes 16-gauge steel with a 1¾ inch diameter. Alternatively, a 1 and⅞ inch diameter is utilized.

FIG. 3 is a top plan view showing a Harley-Davidson® OEM exhaust system.In contrast to the exhaust system described with reference to FIG. 1,the Harley-Davidson® OEM exhaust system comprises a stock first exhaustpipe 70, a stock cross-over exhaust pipe 72, and a stock second exhaustpipe 74. The stock first exhaust pipe 70 has an inlet end, an outletend, and a cross-over connection therebetween. The inlet end isconnected to the exhaust port 30 to scavenge each pulse of exhaust gasfrom engine cylinder 22. The stock first exhaust pipe 70 is configuredto route the scavenged pulse of exhaust gas away from the engine 20. Theoutlet end of the stock first exhaust pipe 70 is in flow communicationwith a first muffler 38. The cross-over connection connects the stockfirst exhaust pipe 70 with the stock cross-over exhaust pipe 72.

The stock cross-over exhaust pipe 72 has an inlet end and two outletends. The inlet end is connected to the exhaust port 32 to scavenge eachpulse of exhaust gas from engine cylinder 24. One of the outlet ends isconnected to the stock first exhaust pipe 70 at the cross-overconnection location. The other outlet end is connected to the stocksecond exhaust pipe 74. The stock cross-over exhaust pipe 72 isconfigured to route the scavenged pulse of exhaust gas away from theengine 20 and towards both of its outlet ends.

The stock second exhaust pipe 74 is in flow communication with the stockcross-over pipe 72 and a second muffler 40. The second muffler 40 isconfigured to exhaust the pulse of exhaust gas received from the stocksecond exhaust pipe 74 into the atmosphere.

In one embodiment of the invention, as illustrated in FIG. 4, aHarley-Davidson® motorcycle 60 is shown with the upstream pipe 42 fromFIG. 2 incorporated into the Harley-Davidson® OEM exhaust system of FIG.3. A feature of this embodiment is that the OEM exhaust system ispartially retained. Portions of the OEM exhaust system which route theexhaust gases from both cylinders 22, 24 to the mufflers 38, 40 areincorporated into the exhaust system shown in FIG. 4. Referring back toFIGS. 1 and 3, the upstream pipe 42 can connect with the stock secondexhaust pipe 74 of the Harley-Davidson® OEM exhaust system. Moreover, anOEM bracket located under the rider's seat is used to attach theupstream pipe 42 to the motorcycle 60. The stock second exhaust pipe 74can route the pulses of exhaust gas from the upstream pipe 42 to themuffler 40. Alternatively, the stock second exhaust pipe 74 is replacedwith the downstream pipe 44 (see FIG. 1).

Referring to FIG. 3, the stock first exhaust pipe 70 which routes thepulses of exhaust gas from cylinder 22 to the muffler 38 is retainedwith a slight modification. This modification requires a tubular section(not shown) to be installed where the stock first exhaust pipe 70connects with the stock cross-over pipe 72. Alternatively, the stockfirst exhaust pipe 70 is removed and replaced with the first exhaustpipe 34.

FIG. 5 is a side perspective view of a portion of the motorcycle exhaustsystem encompassed within line 5 of FIG. 4 and shows the upstream pipe42 of the present invention connected to the cylinder 24. The upstreampipe 42 routes the pulses of exhaust gas under seat 62 and towards theopposite side of the motorcycle 60.

FIG. 6 is a side perspective view of the upstream pipe 42 from FIG. 2,taken on the opposite side of the motorcycle to that of FIG. 4. Theembodiment of the upstream pipe 42 illustrated in FIG. 6 has a lengthalong a lower dimension that ranges from 6.27 to 7.28 inches. In oneadvantageous embodiment where the upstream pipe 42 was incorporated intothe Harley-Davidson® motorcycle 60, the length was measured to be 6.775inches. The upper dimension can range from 4.69 to 5.69 inches. In oneembodiment, the upper dimension was measured to be approximately 5.19inches. However, embodiments of the upstream pipe 42 are not so limitedto the embodiments described herein. The upper and lower dimensions aresubstantially parallel to the centerline 33 (see FIG. 1).

FIG. 7 is a front perspective view of the upstream pipe 42 from FIG. 2,as installed on the motorcycle of FIG. 4 showing the first elbow 46 andthe first sub-elbow 50 lying in different planes. The width of theupstream pipe 42, as measured in as direction that is perpendicular tothe centerline 33 (see FIG. 1), ranges from approximately 9.27 to 10.27inches. In one advantageous embodiment where the upstream pipe 42 wasincorporated into the Harley-Davidson® motorcycle 60, the width of theupstream pipe was measured to be 9.77 inches.

FIG. 8 is a rear perspective view of the upstream pipe 42, from FIG. 2,as installed on the motorcycle of FIG. 4 showing the first sub-elbow 50and the second sub-elbow 52 lying in different planes. The third elbow53 is shown routing the pulse of exhaust gas from the first side of theengine 20 (see FIG. 1) and towards the centerline 33 (see FIG. 1). Aspreviously described with reference to FIG. 2, one embodiment of thethird elbow 53 has an arc length of 75 degrees.

As illustrated in FIG. 8, the distance between an upper surface of thefirst elbow 46 and a weld location between the first elbow and the firstsub-elbow 50 ranges from 1.41 to 2.41 inches. In one advantageousembodiment where the upstream pipe 42 was incorporated into theHarley-Davidson® motorcycle 60, this distance was measured to be 1.91inches. As illustrated in FIG. 7, the distance between an upper surfaceof the third elbow 53 and a lower surface of the second elbow 48 rangesfrom 7 to 8 inches. In one advantageous embodiment where the upstreampipe 42 was incorporated into the Harley-Davidson® motorcycle 60, thisdistance was measured to be 7.5 inches.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described embodimentis to be considered in all respects only as illustrative and notrestrictive and the scope of the invention is, therefore, indicated bythe appended claims rather than the foregoing description. All changeswhich come within the meaning and range of equivalency of the claims areto be embraced within their scope.

1. A motorcycle exhaust system for receiving exhaust gases on a sameside of the motorcycle and discharging the received exhaust gases onboth sides of the motorcycle over an entire RPM range of the motorcycle,said system comprising: a first exhaust pipe in flow communication witha first cylinder for receiving and routing a first pulse of exhaust gassubstantially along only a first side of the motorcycle over the entireRPM range; and a second exhaust pipe in flow communication with a secondcylinder for receiving and routing an entire second pulse of exhaust gasfrom the first side of the motorcycle and to a second side of themotorcycle over the entire RPM range, wherein the first side and thesecond side are located on different sides of a vertical plane passingthrough a centerline of the motorcycle.
 2. An exhaust system accordingto claim 1, wherein the first cylinder and the second cylinder arearranged in a V-Twin configuration, and wherein the vertical planepasses through the first cylinder and the second cylinder.
 3. An exhaustsystem according to claim 1, wherein the second exhaust pipe comprises abend of at least 180 degrees.
 4. An exhaust system according to claim 3,wherein the bend is located on the first side of the motorcycle.
 5. Anexhaust system according to claim 3, wherein the bend is substantiallycontinuous.
 6. An exhaust system according to claim 1, wherein thesecond exhaust pipe is configured to attach to an original equipmentmanufacturer (OEM) attachment point of the motorcycle.
 7. An exhaustsystem according to claim 1, further comprising a first mufflerconnected to and in flow communication with the first exhaust pipe, anda second muffler connected to and in flow communication with the secondexhaust pipe.
 8. An exhaust system according to claim 1, wherein thesecond exhaust pipe comprises an upstream pipe and a downstream pipe,wherein the upstream pipe is in communication with the second cylinderand routes the second pulse of exhaust gas from the first side of themotorcycle chassis and towards the second side, and wherein thedownstream pipe is in flow communication with the upstream pipe andfurther routes the second pulse of exhaust gas along the second side ofthe motorcycle.
 9. An exhaust system according to claim 8, wherein theupstream pipe comprises a first elbow in flow communication with thesecond exhaust port.
 10. An exhaust system according to claim 9, whereinthe upstream pipe comprises a second elbow in flow communication withthe first elbow.
 11. An exhaust system according to claim 10, whereinthe second elbow comprises a first sub-elbow and a second sub-elbow, andwherein the second sub-elbow is in flow communication with the firstsub-elbow.
 12. An exhaust system according to claim 1, wherein thelength of the first exhaust pipe and the length of the second exhaustpipe are approximately equal.
 13. An exhaust system according to claim1, wherein the length of the first exhaust pipe is within 10% of thelength of the second exhaust pipe.
 14. A motorcycle having a firstcylinder and a second cylinder, and a dual exhaust system configured forreceiving exhaust gas pulses from the first and second cylinders on onlya first side of the motorcycle and routing only the exhaust gas pulsesreceived from the second cylinder through the motorcycle and along asecond side of the motorcycle over an entire engine operating range ofthe motorcycle, wherein the first side and the second side are locatedon different sides of the motorcycle.
 15. A motorcycle according toclaim 14, wherein the dual exhaust system comprises a first exhaust pipeand a second exhaust pipe, both exhaust pipes being of approximatelyequal length.
 16. A motorcycle according to claim 15, wherein the lengthof the second exhaust pipe is within 10% of the length of the firstexhaust pipe.
 17. A motorcycle according to claim 14, wherein the secondexhaust pipe comprises a bend of at least 180 degrees.
 18. A motorcycleaccording to claim 17, wherein the bend is located on the first side ofthe motorcycle.
 19. A motorcycle comprising: a frame; an engine attachedto the frame and having a first cylinder head and a second cylinderhead, each containing a cylinder, wherein the first and second cylinderheads exhaust gas on a same side of the engine; and a dual exhaustsystem in flow communication with the two cylinder heads and configuredto route exhaust gases separately to different sides of the frame overan entire RPM range of the engine.
 20. A motorcycle according to claim19, wherein the dual exhaust system further comprises: a first exhaustpipe having a first inlet end and a first outlet end, wherein the firstinlet end is connected to the first cylinder for scavenging and routingexhaust gas away from the first cylinder; and a second exhaust pipehaving a second inlet end and a second outlet end, wherein the secondinlet end is connected to the second cylinder for scavenge and routingexhaust gas through the frame, wherein exhaust gases routed through thefirst and second exhaust pipes are separate from one another.